Voltage-controlled oscillators (VCOs) are commonly used to produce an oscillating signal that oscillates at a desired frequency in response to an applied voltage (or control voltage). For example, phase-locked loops (PLLs) may utilize a VCO to generate a signal having a particular oscillation frequency. In most systems, the VCO is designed to accommodate a range of possible oscillation frequencies over a predetermined input voltage range. Many VCOs include a number of transistors and/or other semiconductor devices, such as varactors, suitably configured to create an electronic oscillator. However, process, voltage, and temperature (PVT) variations may affect the operating parameters for the components that comprise the VCO, which in turn, affect the range of oscillation frequencies achievable by the VCO over the input voltage range. For example, with conventional cross-coupled VCO topologies that utilize varactors to tune the oscillation frequency, variations in the supply voltage may undesirably vary the capacitance of one or more of the varactors, thereby reducing or otherwise shifting the range of oscillation frequencies that the VCO is capable of oscillating at. As the supply voltage is reduced, the effects of supply voltage variations are exacerbated. Another concern is how different types of amplifying devices can be accommodated.